no scales on feet

One of my chickens has no scales on her feet. I am sure that she had some when I got her 6 weeks ago. I have been putting vaseline on her feet for a few days but I think that she has lost more scales. Her feet look pink and sore, but the skin is dry until I put the vaseline on. She is in a pen on grass most of the time, but I let her out to scratch in the garden sometimes. The other hen has her scales.
I have a picture, but don't know how to get it on here.

Thanks davecash and rosyposyosy. I will keep on with the vaseline and perhaps try cooking oil too. My two do go where wild birds go so this may be a long term problem.
I think that my hen may be itchy and picking off her scales. The other does not seem to be affected, but I will treat her too.
I have a problem handling my birds, but I have found that if I put a bowl of her favourite seed on a table and put her next to it she will stand still for a few minutes while I do the job.